KABUL (Reuters) -- Afghanistan's mainly UN-appointed election watchdog has said it had found "clear and convincing evidence of fraud" in last month's presidential election and ordered a partial recount.

The Electoral Complaints Commission (ECC) said in a statement returns must be recounted and audited for any polling station where more than 600 votes, representing 100 percent of "expected" turnout, were cast.

They must also be recounted in any polling station where a candidate received more than 95 percent of the votes if more than 100 valid ballots were cast, the ECC said.

"In the course of its investigations, the ECC has found clear and convincing evidence of fraud in a number of polling stations," the ECC statement said.

Most of the stations where it found fraud had either a larger than expected number of votes cast or a higher than expected proportion cast for a single candidate in the August 20 poll, the ECC said.

"The ECC also noted that the overwhelming majority of stations in which it found fraud had a number of ballots cast that were far in excess of what could be expected based on credible observer reports of low voter turnout," the ECC said.

The ECC is led by a Canadian and three of its five members were appointed by the United Nations.